The invention relates to guide bearings that are suited for use with machinery that operates in whole or in part in a clean environment, and which may be thoroughly cleaned and decontaminated or sterilized prior to and after use.
Such machinery may, for example, be used for processing pharmaceutical components (e.g., vials, ampules or syringes) or in connection with food processing. Machinery of this type necessarily operates in a clean environment, either by placing the entirety of the machine in a clean room or by defining a clean or isolation zone within the machine itself in which the processing operations take place.
In either case, the various processing operations are typically accomplished through the use of mechanical apparatus that includes both stationary and moving components. To ensure that the processing operation is free from contaminants, it is essential that all surfaces of the apparatus within the clean zone, both stationary and moving, are cleaned and decontaminated or sterilized before the operation begins.
The use of a clean zone forming part of the machinery and which houses only the processing operations greatly reduces the difficulty of cleaning the entire machine. Nevertheless, all of the mechanisms within the clean zone must be decontaminated periodically, and difficulties arise particularly with regard to movable mechanical components that serve a processing function.
For example, certain operations within the clean zone may require linear reciprocating actuators which are guided by some type of bearing. Conventional guide bearings must be enclosed, at least in part, which makes them difficult to clean and therefore vulnerable to the collection of contaminants. This problem is conventionally dealt with by a seal such as a rubber bellows or boot that is connected between the reciprocating actuator and the bearing housing. While such devices serve well in shielding from contaminants, they are difficult to clean and also subject to wear over time. If the bellows or boot fails, the clean zone is immediately subject to contamination, and the processing line must be shut down while the seal is replaced. The same problems occur with rotary actuators.
The subject invention is the result of an endeavor to develop linear and rotary guide bearings usable within the clean zone of a processing machine which not only provide the intended guiding function but which are also easily cleanable in their entirety. The inventive bearings of the preferred embodiment are disclosed in conjunction with a machine that performs one step in a hypodermic syringe filling operation, but the inventive principle itself has wider application.
For linear actuators, the inventive bearing of the preferred embodiment specifically takes the form of a pair of spool members carried on a reciprocating shaft that are axially spaced by a predetermined distance. Each of the spools has an associated guide bearing surface, which in the preferred embodiment takes the form of a cylindrical bore formed in a member which is stationary in relation to the movable spool. The cylindrical bores are also axially spaced but by an amount that is greater than the axial spacing between the two spool members.
This relative axial spacing is chosen so that both spool members may be in partial guided engagement with the associated guide bearing surfaces with the actuator shaft in an intermediate position, but when the shaft is in either of its extreme positions, one spool member is in complete engagement with its associated guide bearing surface while the other spool member is moved entirely out of engagement with its associated guide surface. In the opposite extreme position, the spool members are conversely positioned.
This component arrangement ensures that the linearly moving actuator shaft is always in guided engagement by one or both spool members, thus providing the necessary guiding function. However, it will also be appreciated that the spool which is in the free position and its associated guide bearing surface may be cleaned and decontaminated or sterilized in their entirety with a disinfecting solution or sterilizing agent, and with the actuator shaft moved to its opposite limit position, the other spool member and its associated guide bearing surface may be cleaned and decontaminated or sterilized in the same manner.
The inventive principle also is applicable to rotary guide bearings. The preferred embodiment of this device takes the form of a rotatable shaft disposed within a guide housing. The shaft includes first and second spools, with each spool defining at least two radially outwardly projecting lobes (four equiangularly spaced lobes in the preferred embodiment). The guide housing includes a like number of radially inwardly projecting guide surfaces. With the lobes in guided contact with the associated guide bearing surfaces, fluid communication (e.g., passages for disinfecting liquid or a sterilizing agent) exists only through spaces between the lobes. However, when the shaft is rotated and the lobes are out of guided engagement with the associated guide bearing surfaces, all surfaces of both the spool and the guide housing are exposed for cleaning and decontamination. The second spool is axially spaced from the first spool and has the same structural configuration. However, its lobes are angularly disposed in a staggered arrangement relative to the lobes of the first spool; e.g., the four lobes of one spool are disposed at a relative angular difference of 45.degree. to the other. Stated otherwise, when the lobes of the first spool are in full engagement with the associated guide surfaces, the lobes of the second spool have moved entirely out of engagement with their associated guide bearing surfaces.
From the standpoint of cleaning and decontamination, the rotary bearing operates in the same manner as the reciprocating bearing. In other words, the "free" spool and its associated guide bearing surfaces may be cleaned and decontaminated or sterilized with the shaft in the first position, and when the shaft is rotated to a second position (e.g., 45.degree. for four-lobed spools), the other spool may be cleaned and decontaminated or sterilized in its entirety.
The inventive guide bearings are simple in construction, but provide the necessary guiding function throughout all phases of operation. Most importantly, they are capable of being cleaned and decontaminated in their entirety by moving the actuator from one limit position to the other during the cleaning process.
The invention will be more fully appreciated from the following specification and drawings.